The present invention relates generally to the repair of a dovetail slot in a gas turbine engine disk and, more particularly, to a device for defining a designated flow path through such dovetail slot.
It has been found that heavily cold worked material and other characteristics having the capability to reduce low cycle fatigue in dovetail slots of gas turbine engine disks, and particularly turbine disks which are rotated, may be caused during generation of such dovetail slots. In particular, the disturbed material may be caused by a dull broach tool during formation of the dovetail slot. Conventional methods of removing such disturbed material include milling the dovetail slot or to broach it again. Each of these processes, however, are useful only so long as the tools employed are sharp. Further, a hand deburr operation is typically required, which inherently involves a high risk of creating tool marks in the highly stressed dovetail area.
It is known in the art to utilize a flow of abrasive material on surfaces of gas turbine engine components in order to polish or provide surface finishing thereof. Such operations involve removing only a minimal amount of material (e.g., on the order of 0.0005 inch or 0.5 mil). An example of one such method is disclosed in U.S. Pat. No. 6,183,347 to Shaw, where a stream of pliant shot in a carrier fluid is discharged at a shallow angle of incidence against a plug and an adjoining surface for selective abrasion to provide a step. It will be appreciated therein that the method described is for the selective surface treating of a workpiece and does not involve the removal of material on the order required to remove a disturbed layer of material or shallow cracks.
While the aforementioned methods of removing disturbed material from a gas turbine engine disk are useful for that particular purpose, it would be desirable for such disturbed material to be removed by an abrasive flow process which overcomes the limitations noted above. It would also be desirable for a device to be developed which defines a flow path through the dovetail slot in a manner which permits substantially uniform removal of the material in a surface on a bottom portion thereof without affecting the pressure surface portion of the dovetail slot.
In an exemplary embodiment of the invention, a device for defining a designated flow path through a dovetail slot in a gas turbine engine disk is disclosed, wherein a longitudinal axis extends through the dovetail slot. The device includes a first portion having a bottom section contoured to form the flow path in conjunction with a surface of a bottom portion of the dovetail slot and a second portion shaped to be removably retained in a pressure surface portion of the dovetail slot.